1. Field of the Invention
This invention relates to photographic image forming members, more particularly, to posi-type photosensitive members having a photosensitive layer comprising an azide compound containing in its molecular structure an alkali-soluble group.
2. Description of the Prior Art
Photosensitive compositions for posi-type image forming materials which have been conventionally used include those based on an o-quinone diazide compound, a reaction product between a photosensitive diazonium salt and a heteropolyacid, etc. However, only a few of them have been commercially used except for those based on o-quinone diazides.
As is well known in the art, an o-quinone diazide (which contains in its molecular structure the following unit as a photosensitive functional group) decomposes, when exposed to light, to form an alkali-soluble group according to the following mechanism. See O. Sus, Liebigs Annalen der Chemie, Vol. 556, p. 65 (1944). ##STR1##
Such an o-quinone diazide can be used alone or mixed with other alkali-soluble resinous materials such as phenolformaldehyde resins, copolymers of styrene and maleic anhydride, etc., to improve image durability, the film-forming property of the composition, etc. This compound can be more advantageously used in a homogeneous composition in combination with other additives such as a dyestuff, plasticizer, etc.
However, a resinous material which is blended to raise image durability must not only be compatible with the o-quinone diazide compound but also soluble in an aqueous alkaline developer solution. Since these requirements restrict the range of resin selection, for example, the latter excluding resins such as polyamides, which are insoluble in an alkaline solution, resinous materials used to improve image durability have been limited.
In the past, azide compounds have been used as a photo cross-linking agent which decomposes upon exposure to active radiation to effect cross-linking or dimerization, and such have been widely used for nega-type photosensitive compositions. On the other hand, there have only been a few examples where azide compounds have been utilized in posi-type compositions. One example is given in "Light Sensitive Systems" by J. Kosar (John Wiley & Sons, Inc.) p.333, in which an azide compound having an alkoxy group is used which forms a photodecomposition product of greater solubility than the original compound in a dilute alkali, thus being used for posi-type printing plate.